Silylated compositions, and deuterated hydroxyl squaraine compositions and processes

ABSTRACT

Disclosed are novel silylated hydroxyl squaraine compositions, novel deuterated hydroxyl squaraine derivatives, and processes for the preparation thereof. More specifically, there is disclosed a process for the preparation of photoconductive hydroxyl squaraine pigment compositions useful as visible and near infrared photoconductor materials comprising (1) effecting functionalization of the hydroxyl squaraine in an organic solvent system wherein the hydroxyl groups therein are silylated, and (2) subjecting the resulting silylated products to hydrolysis enabling conversion to purified squaraine compositions, or conversion to deuterated hydroxyl squaraine derivatives. The hydroxyl squaraine compositions obtained are useful, for example, as photogenerating pigments in layered imaging members.

BACKGROUND OF THE INVENTION

This invention relates generally to new compositions of matter andimproved processes for the preparation thereof. More specifically, thepresent invention is directed to novel silylated hydroxyl squarainecompositions, novel deuterated hydroxyl squaraine derivatives, and toprocesses for preparing these compositions. The silylated products areprimarily useful as colorants, and as intermediates for the preparationof hydroxyl squaraine derivatives, while the deuterated hydroxylsquaraine derivatives are useful as photoconductive compositions. Thus,for example the hydroxyl squaraines obtained from the silylated productsof the present invention can be incorporated into layeredphotoresponsive imaging members, or devices, which members areresponsive to visible light, and infrared illumination orginating inlaser printing systems. The photoresponsive members envisioned can, forexample, contain situated between a bottom photogenerating layer and atop hole transport layer, or situated between a top photogeneratinglayer and a bottom hole transporting layer and a supporting conductivesubstrate, a photoconductive composition, comprised of the squarainecompositions, especially the deuterated and nondeuterated hydroxylsquaraine derivatives prepared from the silylated products illustratedherein. Examples of other photoresponsive devices include thosecomprised of a conductive substrate, a hole transport layer, and as atop layer photoconductive hydroxyl squaraine derivatives; or wherein thephotoconductive squaraine layer is situated between a conductivesubstrate and a hole transport layer. The photoconductive squarainecompositions are partially or totally responsible for enhancing theintrinsic properties of the photogenerating layer in the infrared andvisible regions of the spectrum, thereby allowing the resulting imagingmembers to be sensitive to infrared and/or visible light.

Additional photoresponsive devices include those containing thephotoconductive squaraine compositions in contact with a hole transportlayer deposited on a supporting substrate with optional blocking andadhesive layers, and a protective top layer; or a similar device whereinthe photoconductive layer is situated between the hole transport layer,and a supporting substrate. Other specific photoconductive devicesincluded within the scope of the present invention are those comprisedof a supporting substrate, an optional blocking layer, a photogeneratinglayer containing inorganic photoconductive materials, such as trigonalselenium, or organic photoconductive materials includingphthalocyanines, a photoconductive layer comprised of the hydroxylsquaraine compositions, and a top hole transport layer. In a variationof the latter device, the hydroxyl squaraine photoconductive materialcan be located on the supporting substrate, or between the holetransport layer and the photogenerating layer. Several of these devicesare illustrated in U.S. Pat. No. 4,415,639 entitled LayeredPhotoresponsive Devices, the disclosure of which is totally incorporatedherein by reference.

Photoconductive imaging members containing certain squarainecompositions, particularly hydroxyl squaraines, are known, as describedfor example in U.S. Pat. Nos. 3,617,270 and 3,824,099. Further, there isdescribed in a review article by Arthur H. Schmidt, SYNTHESIS, pages.961-994, 1980 and the references therein, several methods for preparingsquaric acid and squaraine derivatives including hydroxyl squaraines.Also known are layered photoresponsive devices with photogeneratinglayers and transport layers, reference U.S. Pat. No. 4,265,990. Examplesof photogenerating layers disclosed in this patent include trigonalselenium, and phthalocyanine derivatives, while examples of transportlayers that may be selected include certain aromatic amines and aromaticdiamines dispersed in a resinous binder composition. Moreover, the useof specific squaraine pigments in photoresponsive imaging devices wasdisclosed in U.S. Pat. No. 4,415,639 entitled Layered PhotoresponsiveDevices wherein there is described an improved photoresponsive devicecontaining a substrate, a hole blocking layer, an optional adhesiveinterface layer, an inorganic photogenerating layer, a photoconductivecomposition capable of enhancing the intrinsic properties of thephotogenerating layer, and a hole transport layer. As photoconductivecompositions for these devices, there can be selected various hydroxylsquaraine pigments. Additionally, there was disclosed in U.S. Pat. No.3,824,099 certain photosensitive hydroxyl squaraine compositions.According to the disclosure of this patent, the squaraine compositionsare photosensitive in normal electrophotographic imaging systems.

In a copending application, there are described novel squarainecompositions of matter, including bis-9-(8-hydroxyjulolidinyl)squaraine,and the use of these compositions in imaging members. One of the imagingmembers illustrated contains a supporting substrate, a hole blockinglayer, an optional adhesive interface layer, an inorganicphotogenerating layer, a julolidinyl photoconducting composition layercapable of enhancing the intrinsic properties of the photogeneratinglayer and a hole transport layer.

Processes for preparing squaraine compositions generally involve thereaction of squaric acid with an aromatic amine. Thus, for example, thejulolidinyl squaraine compositions can be prepared by the reaction of anaromatic amine and squaric acid, in a molar ratio of from about 1.5:1 to3:1 in the presence of a mixture of an aliphatic alcohol, and anoptional azeotropic cosolvent. About 200 milliliters of alcohol to 0.1mole of squaric acid are used, while from about 40 milliliters to about4,000 milliliters of an azeotropic material, such as benzene, toluene,or the like are selected. The squaric acid coupling reaction isgenerally accomplished at a temperature of from about 50 degreesCentigrade to about 130 degrees Centigrade. Illustrative examples ofaromatic amine reactants include 8-hydroxyjulolidine,3-dimethylaminophenol 3-diethylaminophenol and the like while examplesof aliphatic alcohols include 1-butanol, 1-pentanol and 1-octanol.

Additionally, there is described in another copending application thepreparation of novel squaraine compositions, including for example,bis(4-N,N-dimethylamino-2-hydroxy-6-methylphenyl)squaraine by thereaction of squaric acid and3-hydroxy-5-methyl-N,N-dimethylaniline(3-N,N-dimethylamino-5-methyl-phenol).More specifically, as disclosed in this copending application thesquaraine compositions involved are prepared by suspending squaric acidin an alcohol, followed by heating. Subsequently, there is then added tothe resulting mixture an aromatic amine, such as3-dialkylaminomethylphenol. This reaction is generally accomplished at atemperature of from about 50° C. to about 130° C. with stirring, whereinthe desired product is isolated from the reaction mixture by knowntechniques and identified by analytical tools including NMR, massspectroscopy and elemental analysis for carbon, hydrogen, oxygen andnitrogen.

While the above processes for preparing squaraine compositions may besuitable for their intended purposes, there continues to be a need forother processes wherein squaraine compositions, useful asphotoconductive materials, can be prepared. Additionally, there remainsa need for simple, economical processes for preparing squarainecompositions, wherein the squaraine products obtained are of higherpurity, and smaller particle size than those obtained with many of theprior art processes. It is believed that the presence of impurities inthe squaraine compositions causes the photosensitivity of thesecompositions to vary significantly, and in many instances, to be lowerthan the squaraine compositions prepared in accordance with the processof the present invention. Further, there continues to be a need forprocesses for the preparation of squaraine compositions, especiallyhydroxyl squaraines, of high purity, small pigment particle size, andimproved morphological properties which, when selected for layeredphotoresponsive imaging devices, allow the generation of acceptableimages, and wherein such devices can be repeatedly used in a largenumber of imaging cycles without deterioration thereof from the machineenvironment or surrounding conditions. Moreover, there remains a needfor certain squaraine compositions, wherein the resulting products whenincorporated into imaging members exhibit excellent pigment dispersionwith uniform surface coverage, and superior sensitivity. Additionally,there is a need for processes for the preparation of photosensitivepigments containing novel deuterated hydroxyl squaraines. There alsocontinues to be a need for processes of preparing hydroxyl squaraines,and novel deuterated hydroxyl squaraines, which possess highphotosensitivity characteristics and desirable small particle sizes,enabling their use as photosensitive pigments with increased andconsistent photosensitivity. Moreover, there remains a need for novelsilylated products, which subsequent to hydrolysis are converted intodeuterated and nondeuterated hydroxyl squaraine derivatives as indicatedherein.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide improvedprocesses for preparing squaraine compositions.

In another object of the present invention there are provided methodsfor the functionalization of photoconductive squaraine compositionscontaining hydroxyl groups, enabling silylated products with enhancedsolubility in organic solvents.

In yet another object of the present invention, there are providedsimple, economical processes for preparing certain squarainecompositions with high purity levels, and less occluded impurities thansimilar hydroxyl squaraine derivatives prepared by several knownmethods.

In still a further object of the present invention, there are providedimproved processes for obtaining squaraine compositions of matter, whichcontain particles of substantially smaller particle sizes than similarhydroxyl squaraines prepared by many known processes.

In another object of the present invention, there are provided improvedprocesses for preparing certain squaraine compositions with enhancedphotosensitivity, good dark decay properties and acceptable chargeacceptance.

In another object of the present invention there are provided improvedprocesses for preparing squaraine compositions, with enhancedphotosensitivity in the visible and near infrared regions of thespectrum.

In yet another object of the present invention there are providedimproved processes for preparing photosensitive pigments with desiredparticle sizes, and improved morphological characteristics, by thecontrolled hydrolysis of silylated hydroxyl squaraine derivativeproducts.

In yet another object of the present invention there are providedimproved methods for preparing novel deuterated photoconductive hydroxylsquaraine derivatives, which are photosensitive in the visible and nearinfrared regions of the spectrum.

In still another object of the present invention there are providedprocesses for the preparation of hydroxyl squaraine derivatives of highpurity and effective small particle sizes, enabling their presence inhigh density in a photoconductive layer, thereby enhancing imageresolution and photosensitivity of the photoreceptor involved.

In a further object of the present invention there are provided novelsilylated compositions of matter which are useful as colorants and whichcan function as intermediates in that subsequent to hydrolysis, thesilylated products are converted to useful hydroxyl squarainederivatives.

These and other objects of the present invention are generallyaccomplished by the provision of novel silylated hydroxyl squarainederivative compositions, improved hydroxyl squaraine derivatives, noveldeuterated hydroxyl squaraine derivatives, processes for preparing thesecompositions, and photoconductive imaging members containing hydroxylsquaraine derivatives and deuterated hydroxyl squaraine derivatives.More specifically, there is provided in accordance with the presentinvention novel silylated compositions, and deuterated hydroxylsquaraine derivatives of the following formulas: ##STR1## wherein R₁ andR₂ are independently selected from alkyl groups, aromatic groups, cyclicgroups, including julolidinyl substituents, and non-cyclic groups,including substituted alkyl groups, X is selected from the groupconsisting of oxygen, sulfur, and selenium, R₃, R₄ and R₅ areindependently selected from hydrogen, alkyl groups, halides, alkoxy,alkyl carboxy, and the like; and R₆, R₇ and R₈ represent appropriategroups attached to siloxyl groups, including alkyl substituents,halogenated substituents, oxygenated substituents, and the like, D is adeuterium atom, R'₁, R'₂, R'₃ and R'₄ are independently selected fromalkyl groups, aromatic groups, cyclic groups, and non-cyclic groups,providing that at least one of these groups is dissimilar, R'₅, R'₆,R'₇, R'₈, R'₉, R'₁₀ and R'₁₁ are independently selected from hydrogen,alkyl groups, halides, alkoxy and alkyl carboxy groups, and R'₁₂, R'₁₃and R'₁₄ are selected from alkyl substituents, halogenated substituents,oxygenated substituents and the like.

The silylated products as indicated herein are useful for example ascolorants in that in solution they absorb light of a wavelength rangingnear 649 nanometers and further these novel compositions can be used asintermediates for the formation of hydroxyl squaraine derivatives by ahydrolysis reaction as illustrated hereinafter. The resulting hydroxylsquaraine derivatives can then be selected as a photoconductive pigmentfor incorporation into a layered photoresponsive device sensitive tovisible light, and/or infrared illumination. Similarly, the noveldeuterated hydroxyl squaraine derivatives obtained by the hydrolysis ofthe silylated compositions, in a deuterated protonic solvent system, areuseful as photoconductive pigments for incorporation into layeredphotoresponsive devices which are sensitive to visible light, and/orinfrared illumination.

Also in accordance with the present invention there is provided asilylation process for the purification of squaraine compositionscontaining hydroxyl functional groups therein. The intermediate productsare of enhanced solubility in various organic solvents, enablingundesirable impurities to be removed therefrom. Subsequent to hydrolysisof the resulting functionalized product in deuterated, or non-deuteratedsolvents, including alcohols, water, and mixtures thereof, there resultsfor example compositions containing less impurities therein than theinitial squaraine reactant. When deuterated solvents are selected, thereis obtained in accordance with the process of the present inventionnovel deuterated hydroxyl squaraine compositions. More specifically inone embodiment, the process of the present invention comprisessilylating certain hydroxyl squaraine compositions with known silylationreagents, at a temperature of from about zero degrees Centigrade toabout 155 degrees Centigrade, resulting in products containing silylether groups thereon including trialkylsiloxyl groups, whichcompositions have improved solubility in organic solvents enabling thepreparation of hydroxyl squaraines or deuterated hydroxyl squaraines, ofimproved purity, and thus improved sensitivity, subsequent tohydrolysis. During this process the undesirable occluded impuritiespresent in the hydroxyl squaraine pigments are released therefrom.Removal of the undesirable soluble impurities can, for example, beachieved by separating the precipitated product from the reactionmixture by known methods. Further, insoluble impurities which may bepresent in the hydroxyl squaraine composition reactant can be separatedtherefrom by dissolving the formed silylated product in halogenatedsolvents, like methylene chloride, chloroform and trichloroethane,followed by filtration and evaporation of the solvent selected. Also thesolution containing the soluble silylated hydroxyl squaraine can bepurified by known chromatographic techniques, and thereafter thepurified silylated derivatives can be isolated therefrom, byevaporation.

Subsequently, the silylated product is hydrolyzed in a suitable solventsystem at an effective temperature so as to result in a hydroxylsquaraine of higher purity than the initial hydroxyl squaraine, andwherein the resulting hydroxyl squaraine composition is of a smalleraverage particle/crystallite size than the initial hydroxyl squarainereactant. Moreover, novel hydroxyl squaraine compositions can beprepared by effecting the hydrolysis in the presence of a deuteratedcomposition enabling the preparation of deuterated hydroxyl squarainesof high purity and small average particle/crystallite sizes.

There is illustrated in the following equations specific examples forpreparing symmetrical silylated products (reactions I and II), hydroxylsquaraine derivatives (reaction III) and deuterated hydroxyl squarainederivatives (reactive IV). This reaction scheme can also be selected forthe preparation of related unsymmetrical compositions. ##STR2## whereinthe substituents are as defined herein.

The hydroxyl squaraine derivatives selected for silylation are generallyderived from the condensation products of hydroxyl aromatic amines, andsquaric acid. More specifically, these hydroxyl squaraine derivativescan be in various isomeric forms, including cis and trans isomers andmay have symmetrical or unsymmetrical groups (mixed squaraines) thereonand attached to the central squaric acid moiety. Moreover, it isimportant to note that the silylation reaction illustrated, and thesubsequent hydrolysis process are applicable to virtually any hydroxylsquaraine derivatives providing they contain therein a functionalizablehydroxyl (--OH) or thio (--SH) group. Thereafter as illustrated theresulting silylated product can be hydrolyzed. Alternatively thesilylated product can be dissolved in a suitable organic solvent whereinthe insoluble impurities are removed, followed by hydrolysis of thesoluble product.

Alkyl substituents include those containing from about 1 carbon atom toabout 10 carbon atoms, and preferably from 1 carbon atom to about 4carbon atoms like methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl,octyl, nonyl and decyl. Preferred alkyl groups are methyl, ethyl, propyland butyl. Examples of alkylcarboxy substituents include methylcarboxy,ethylcarboxy, propylcarboxy, butylcarboxy, and the like. Examples ofaromatic groups include those containing from about 6 to about 24 carbonatoms, such as phenyl, and naphthyl, while alkoxy groups include thosecontaining from about 1 to about 6 carbon atoms, such as methoxy,ethoxy, propoxy, and the like. Illustrative examples of cyclic groupsare julolidinyl substituents, while carboxy groups envisioned includealkylcarboxy, such as methylcarboxy.

Illustrative examples of squaraine compositions with improved purity andother desirable characteristics, including small particle sizes,deuterated squaraine compositions, and novel silylated materialsprepared in accordance with the process of the present invention includeknown hydroxyl squaraine derivatives such asbis(2-hydroxy-4-N,N-dimethylaminophenyl)squaraine,bis(2-hydroxy-4-N,N-diethylaminophenyl)squaraine,bis(2-hydroxy-6-methyl-4-N,N-dimethylaminophenyl)squaraine,bis-9-(8-hydroxyjulolidinyl)squaraine; hydroxyl deuterated squarainederivatives including bis(2-deuteratedhydroxy-4-N,N-dimethylaminophenyl)squaraine, bis(2-deuteratedhydroxy-4-N,N-diethylaminophenyl)squaraine, bis(2-deuteratedhydroxy-6-methyl-4-N,N-dimethylaminophenyl)squaraine, bis-9-(8deuterated hydroxy julolidinyl)squaraine; unsymmetrical squaraines, suchas 2-hydroxy-4-N,N-dimethylaminophenyl-4'-N',N'-dimethylaminophenylsquaraine,2-hydroxy-4-N,N-dimethylaminophenyl-2'-methyl-4'-N',N'-dimethylaminophenylsquaraine,2-hydroxy-4-N,N-dimethylaminophenyl-2'-fluoro-4'-N',N'-dimethylaminophenylsquaraine,2-hydroxy-4-N,N-dimethylaminophenyl-2'-chloro-4'-N',N'-dimethylaminophenylsquaraine; bis(2-trimethylsiloxy-4-N,N-dimethylaminophenyl)squaraine,bis(2-trimethylsiloxy-4-N,N-diethylaminophenyl)squaraine,bis(2-trimethylsiloxy-6-methyl-4-N,N-dimethylaminophenyl)squaraine,bis-9-(8-trimethylsiloxyjulolidinyl)squaraine; and the like.

It is appreciated that the process of the present invention can beselected for the preparation of other squaraine compositions includingsymmetrical and unsymmetrical squaraine derivatives containing forexample, hydroxyl, and/or thiol groups therein. Accordingly, the processof the present invention is not limited to the specific illustrativereactions, or reaction parameters provided.

There can be selected for the silylation reaction known reagents asdescribed in the literature, and the textbook Silylation of OrganicCompounds, by Alan E. Pierce, of Pierce Chemical Company, Rockford,Ill., 1979, the appropriate disclosure of which is totally incorporatedherein by reference. Specific examples of useful silylation reagentsinclude N,O-bis-(trimethylsilyl)-acetamide (BSA),N,O-bis-(trimethylsilyl)trifluoroacetamide (BSTFA),N-methyl-N-trimethylsilyltrifluoroacetamide (MSTFA), N-trimethylsilyldiethylamine (TMSDEA), hexamethyldisilazane (HMDS),trimethylchlorosilane (TMCS), N-trimethylsilylimidazole (TMSI), and thelike.

Known dried organic solvents selected for the silylation reactioninclude dimethylformamide, pyridine, tetrahydrofuran, chloroform,toluene, ethers, dimethylsulfoxide, ethylacetate, and the like. Othersolvents can be selected providing the objectives of the presentinvention are achieved, that is those solvents that will allow thesilylation of the hydroxyl groups to be accomplished without resultingin undesirable side reactions which may permanently degrade or adverselyaffect the physical properties of the reactants and the resultingproducts.

The silylation reaction can be monitored, for example, by infraredspectroscopy using Nujol Mull (mineral oil) as a dispersing medium.Certain IR absorption bands associated with the hydroxyl groups of thesquaraine compositions selected will diminish upon silylationaccompanied by an increase in the intensity of new peaks attributed tothe presence of trimethylsiloxy groups.

Hydrolysis is effected by adding to the separated silylated product aneffective amount of a solvent system comprised of for example waterand/or alcohols and maintaining the resulting mixture at an appropriatetemperature. Additionally, the hydrolysis reaction can be accomplishedin situ by initially dispersing the silylated product formed in apolymeric binder, resulting in a film, and subsequently exposing thisfilm to a hydrolysis solvent or its vapor. For causing the formation ofthe novel deuterated hydroxyl squaraine compositions of the presentinvention, hydrolysis is effected in substantially an identical mannerwith the exception that there is selected as the hydrolysis reactant, adeuterated material as illustrated hereinafter. Thus, when thehydrolysis of the silylated squaraine composition or silylated squarainederivatives is effected in the presence of a solvent system containingdeuterated water or deuterated alcohols there are obtained the noveldeuterated hydroxyl squaraine derivatives as illustrated hereinbefore.These deuterated compositions can be incorporated as photoconductivepigments, for example, in photoresponsive devices similar to the devicesillustrated herein with respect to the hydroxyl squaraine compositions.

The amount of silylation reactants selected is dependent upon a numberof factors, including the specific reactants and solvents selected, thereaction temperature, the degree of purity of squaraine product desiredand other reaction parameters involved. Generally, however, a slightexcess of the theoretical amount of silylation reagent is used toachieve complete functionalization of the hydroxyl group or groupscontained in the starting squaraine reactant. However, partialsilylation of the hydroxyl squaraine reactants, followed by hydrolysis,can also be effected to obtain the hydroxyl squaraines of improvedpurity. Additionally, an effective but minimum amount of solvent isutilized to achieve the silylation reaction and to maximize yield ofproduct. This amount, ranges for example, from about 5 milliliters toabout 80 milliliters, and preferably from about 5 milliliters to about35 milliliters for each gram of selected hydroxyl squaraine. Also, thehydrolysis of the silylated squaraine derivatives can be effected in aselected solvent system at an optimum temperature in order that theresulting reverted hydroxyl squaraine derivatives will have desirableparticle sizes and improved morphological characteristics. Thetemperature selected for the silylation and hydrolysis can likewise varydepending on the other reaction parameters, generally however thesilylations are accomplished at a temperature of from about zero degreesCentigrade to about 200 degrees Centigrade, while the hydrolysisreactions are accomplished at a temperature of from about -20 degreesCentigrade to about 120 degrees Centigrade

The resulting products subsequent to the hydrolysis from the reactionmixture can be isolated and purified by various known techniques,including for example filtration, washing, evaporation, andcrystallization. These products were characterized primarily byelemental analysis data, infrared analysis, NMR analysis, visibleabsorption spectroscopy and microscopy techniques including scanningelectron microscopy, transmission electron microscopy andphotomicroscopy. Additionally, the chemical composition data generatedfrom these techniques were substantially equivalent to the dataavailable for the identical compounds prepared from the squaric acidprocess.

The hydroxyl squaraine derivatives, and deuterated hydroxyl squarainederivatives prepared in accordance with the process of the presentinvention are of a small particle size ranging in diameter of from aboutless than 0.1 microns to about less than 1.0 microns. Small particlesizes enable the superior dispersion of these products in resinousbinder compositions, thereby allowing excellent uniform photoconductivepigment coverage, high image resolution, good charge acceptance andsuperior photosensitivity for imaging devices containing thesecompositions, as compared to similar hydroxyl squaraines prepared by theknown squaric acid process.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention and further featuresthereof reference is made to the following detailed description ofvarious preferred embodiments wherein:

FIGS. 1 to 4 (configurations 1 to 4 respectively) are schematiccross-sectional views of photoresponsive devices of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

There is illustrated in FIG. 1 (configuration 1) a photoresponsivedevice comprised of a supporting substrate 1, an optional blocking layer3, an optional adhesive layer 5, a photoconductive layer 7, comprised ofthe purified hydroxyl squaraine compositions prepared in accordance withthe present invention, optionally dispersed in a resinous binder 10, andas a top layer 9, a charge transport or hole transport layer containinga transporting composition, such as an aromatic amine or an aromaticdiamine, dispersed in a resinous binder composition, 11.

Illustrated in FIG. 2 (configuration 2) is a photoresponsive devicecomprised of a conductive substrate 17, such as aluminized Mylar, a holetransport layer 19, containing a material which will transport holes,including aromatic diamines and aromatic amines dispersed in a resinousbinder 20, a photoconductive layer 21, comprised of the squarainecompositions prepared in accordance with the process of the presentinvention, optionally dispersed in a resinous binder, 23 and an optionalprotective overcoating layer 25.

Illustrated in FIG. 3 (configuration 3) are photoresponsive devicesuseful in imaging and printing systems, comprised of a conductivesubstrate 31, an optional blocking layer 33, an optional adhesive layer35, a photogenerating layer 37 comprised of inorganic or organicphotogenerating pigments, optionally dispersed in a resinous binder 38,these pigments including metal phthalocyanines, metal freephthalocyanines, vanadyl phthalocyanines, selenium, selenium alloys,trigonal selenium and the like, layer 39 comprised of the squarainecompositions prepared in accordance with the process of the presentinvention, optionally dispersed in a resinous binder 40, and a chargetransport layer 41, comprised of materials which will enable thetransport of positive charges, including aromatic diamines and aromaticamines dispersed in resinous binder compositions, 42.

In FIG. 4, (configuration 4) there is illustrated a furtherphotoresponsive device of the present invention comprised of aconductive supporting substrate of, for example, aluminized Mylar 51, anoptional blocking layer 53, an optional adhesive layer 55, aphotoconductive layer 57, comprised of the squaraine compositionsprepared in accordance with the process of the present invention,optionally dispersed in a resinous binder 59 a photogenerating layer 60,comprised of organic photoconductive pigments or inorganicphotoconductive pigments, optionally dispersed in a resinous binder 61,and as a top layer 63, a charge transporting substance, including anaromatic diamine or an aromatic amine dispersed in a resinous binder 64.

When incorporated into xerographic imaging and printing systems thedevices of FIGS. 1, 3 and 4 are subjected to negative charging on thesurface, while the device of FIG. 2 is positively charged.

Similar photoresponsive imaging members, and devices, as well asadditional members are described for example in copending applicationsU.S. Pat. No. 4,508,803 entitled Overcoated Photoresponsive Devices, andU.S. Ser. No. 558,246/83 entitled Photoconductive Devices ContainingNovel Squaraine Compositions, with the exception that in the copendingapplications the squaraines are not prepared in accordance with theprocess of the present invention. The disclosure of each of thecopending applications is totally incorporated herein by reference.Moreover illustrative examples of materials that can be selected foreach of the layers described in the Figures, as well as the thicknessesof these layers are disclosed in the referred to copending applications.

Preferred materials for the photogenerating pigments include metalphthalocyanines, metal-free phthalocyanines, and trigonal selenium,while preferred hole transport molecules are comprised of the diaminecompositions as illustrated in the copending applications. Morespecifically examples of amine hole transport compositions areN,N'-diphenyl-N,N'-bis(alkylphenyl)-[1,1-biphenyl]-4,4'-diamine whereinalkyl is selected from the group consisting of methyl, such as 2-methyl,3-methyl and 4-methyl, ethyl, propyl, butyl, hexyl and the like. Withchloro substitution, the amine isN,N'-diphenyl-N,N'-bis(halophenyl)-[1,1'-biphenyl]-4,4'-diamine whereinthe halo atom is 2-chloro, 3-chloro or 4-chloro. Resinous bindersselected include materials such as those described in U.S. Pat. No.3,121,006 the disclosure of which is totally incorporated herein byreference. Specific examples of organic resinous materials includepolycarbonates, acrylate polymers, vinyl polymers, cellulose polymers,polyesters, polysiloxanes, polyamides, polyurethanes and epoxies as wellas block, random or alternating copolymers thereof. Preferredelectrically inactive binder materials for the transport layer arepolycarbonate resins having a molecular weight (Mw) of from about 20,000to about 100,000 with a molecular weight in the range of from about50,000 to about 100,000 being particularly preferred. Generally, theresinous binder contains from about 10 to about 75 percent by weight ofthe hole transport material, and preferably from about 35 percent toabout 50 percent of this material. Preferred binder compositions for thephotogenerating, or photoconductive layers include polyesters,polyvinylbutyral, Formvar®, polycarbonate resins, especially thosecommercially available as Makrolon®, polyvinyl carbazoles, epoxy resins,phenoxy resins, commercially available as poly(hydroxyether) resins, andthe like.

Examples of overcoating layers for the imaging members illustrated areselenium alloys, silicone hardcoatings, and other related compositions.This layer can be of a thickness of from about 1 micron to about 2microns.

The supporting substrates for the imaging members described may comprisea layer of insulating material such as an inorganic or organic polymericmaterial, a layer of an organic or inorganic material having aconductive surface layer thereon, or a conductive material such as, forexample, aluminum, chromium, nickel, indium, tin oxide, brass or thelike. Also there can be coated on the substrate as optional layers knownhole blocking layers, like silane compositions, and an adhesivematerial, such as a polyester resin, commercially available for examplefrom Goodyear Chemical Company. The substrate may be flexible or rigidand may have any of many different configurations, such as for example,a plate, a cylindrical drum, a scroll, an endless flexible belt and thelike. Preferably, the substrate is in the form of an endless flexiblebelt.

The photoreceptor devices can be prepared by a number of known methods,reference for example the copending applications indicated, the processparameters and the order of coating of the layers being dependent on thedevice desired. Thus, for example, a multilayered photoreceptor devicecan be prepared by vacuum sublimation or various solution coatings ofthe photoconducting layer on a supporting conductive substrate, with orwithout a blocking layer, and an interface adhesive layer, andsubsequently depositing by solution coating the hole transport layer. Inanother process variant, the layered photoreceptor device can beprepared by providing the conductive substrate possessing a holeblocking layer and an optional adhesive layer, and applying thereto bysolvent coating processes including solution spray coating, draw barcoating processes, laminating processes, or other methods, aphotogenerating layer, a photoconductive composition comprised of thesquaraines of the present invention, which squaraines are capable ofenhancing the intrinsic properties of the imaging member in the infraredand/or visible range of the spectrum, and a hole transport layer.

The improved photoreceptor devices of the present invention can beincorporated into various imaging systems, including conventionalxerographic imaging processes. Additionally, the improved photoreceptordevices of the present invention containing an inorganic photogeneratinglayer, and a photoconductive layer comprised of the hydroxyl squarainesof the present invention can function in imaging and printing systemswith visible light and/or near infrared light. In this embodiment, theimproved photoresponsive devices of the present invention may be eithernegatively charged or positively charged, depending on the configurationof the photoreceptor, exposed to light in a wavelength of from about 300to about 950 nanometers, either sequentially simultaneously, orselectively, followed by developing the resulting image, andtransferring to paper or other substrates. The above sequence may berepeated many times.

The invention will now be described in detail with reference to specificembodiments thereof, it being understood that these examples areintended to be illustrative only. The invention is not intended to belimited to the materials, conditions, or process parameters recitedherein, it being noted that all parts and percentages are by weightunless otherwise indicated. Additionally with respect to the workingExamples, as well as the specification and claims, reference to modifiedhydroxyl squaraines refer to compositions prepared by the processdescribed in the present application, while the phrase unmodifiedhydroxyl squaraines refers to materials prepared by the known squaricacid condensation method described in the prior art.

EXAMPLE I

Bis(2-hydroxyl-4-N,N-dimethylaminophenyl)squaraine (OH-Sq, 2.75 grams),N,N-dimethylformamide (DMF, 34.5 ml) andbis(trimethylsilyl)trifluoracetamide (BSTFA, 2.75 grams) were heatedtogether with stirring at 60° C. under an argon atmosphere for 6.0hours. The mixture was cooled to room temperature, and the resultingsolid was collected by vacuum filtration under an argon atmosphere,followed by rinsing the product with a 10 volume percent solution ofanhydrous diethyl ether in hexane. The product was then dried undervacuum at 40° C. for 1.5 hours resulting in 3.70 grams ofbis(2-trimethylsiloxy-4-N,N-dimethylaminophenyl)squaraine (O-TMS-Sq), inthe form of shiny, green-gold crystals.

Found: C, 62.92; H, 7.22, N, 5.89; O, 12.84; Si, 11.05;

Calcd for: C₂₆ H₃₆ N₂ O₄ Si₂ : C, 62.87; H, 7.30; N, 5.64; O, 12.88; Si,11.31.

Infrared (Nujol): New peaks appeared at 914 and 853 cm⁻¹ and peaks at1,400, 888 and 738 cm⁻¹ disappeared. ¹ H-NMR data was consistent withthat of the expected silylated product.

EXAMPLE II

The process of Example I was repeated with the exception that there wasselected as a replacement for the squaraine reactant (OH-Sq)bis(2-hydroxy-4-N,N-diethylaminophenyl)squaraine (OH-Et-Sq, 2.19 grams).Also 35.0 milliliters of DMF and 2.93 grams of BSFTA were used. The timeof reaction was 3.5 hours.Bis(2-trimethylsiloxy-4-N,N-diethylaminophenyl)squaraine (O-TMS-EtSq)3.84 grams was obtained as a green powder.

Found: C, 65.18; H, 8.02; N, 5.05; O, 11.41; Si, 9.96.

Calcd for: C₃₀ H₄₄ N₂ O₄ Si₂ : C, 65.18; H, 8.02; N, 5.07; O, 11.58; Si,10.16.

Infrared (Nujol): New peaks appeared at 1,586, 1,150, 976, 851 and 767cm⁻¹ and peaks at 1,536, 1120 and 956 cm⁻¹ disappeared. ¹ H-NMR data wasconsistent with that of the expected silylated product.

EXAMPLE III

The process of Example I was repeated with the exception that there wasselected as a replacement for the squaraine reactant (OH-Sq),bis(2-hydroxy-6-methyl-4-N,N-dimethylaminophenyl)squaraine (OH-ME-Sq,0.600 grams). Also 8.0 milliliters of DMF, and 0.533 grams of BSFTA wereused. The time of reaction was 5.0 hours.Bis(2-trimethylsiloxy-6-methyl-4-N,N-dimethylaminophenyl)squaraine(O-TMS-MeSq) 0.650 grams was isolated as a green-grey powder.

Infrared (Nujol): New peaks appeared at 1,593, 1,264 and 1108 cm⁻¹ andpeaks at 1,611, 1,235, 1,202, 1095 and 871 cm⁻¹ disappeared. ¹ H-NMRdata was consistent with that of the expected silylated product.

EXAMPLE IV

The squaraine composition prepared in Example I (O-TMS-Sq), 1.50 grams,was stirred with tetrahydrofuran (25 ml) for 5.0 minutes. Methanol,(25.0 ml) and water (1.0 ml) were added to the mixture which was thenstirred at 60° C. for 2.0 hours. The resulting solid was collected fromthe warm mixture by vacuum filtration and rinsed with methanol. Theproduct was dried under vacuum at 60° C. for 2.0 hours yielding 1.11grams of the modified hydroxyl squaraine,bis(2-hydroxy-4-N,N-dimethylaminophenyl)squaraine(OH-Sq), as a blue greypowder.

Found: C, 68.28; H, 5.69; N, 8.02; O, 17.81.

Calcd. for C₂₀ H₂₀ N₂ O₄ : C, 68.17; H, 5.72; N, 7.95; O, 18.16.

Infrared (Nujol) data was identical to that for the unmodified OH-Sq.

Transmission Electron Microscopy (TEM) and photomicroscopy resultsindicate that the modified OH-Sq pigment, prepared in accordance withExample IV contains a high population of fine, acicularparticles/crystallites of aproximately 100 Angstroms width and 1,000Angstroms length and some denser acicular particles/crystallites rangingin length of from 0.2 um to 1.8 um. In contrast, unmodified OH-Sq(obtained from the squaric acid synthesis) has a particle/crystallitesize range of from approximately 1.2 um to 27.5 um in length, asdetermined by TEM and photomicroscopy.

EXAMPLE V

The squaraine composition prepared in Example II, (O-TMS-EtSq, 1.43grams), was stirred with methanol (50 ml) and water (0.1 ml) at 60° C.for 3.5 hours. The resulting solid product was collected from themixture by vacuum filtration, and rinsed with methanol. The product wasthen dried under vacuum at 45° C. for 1.5 hours yielding 1.05 grams ofthe modified bis(2-hydroxy-4-N,N-diethylaminophenyl)squaraine,(OH-EtSq), as a green-gold powder.

Found: C, 70.35; H, 7.06; N, 6.73; O, 15.34;

Calcd for C₂₄ H₂₈ N₂ O₄ : C, 70.57; H, 6.91; N, 6.86; O, 15.67.

Infrared (Nujol) and ¹ H-NMR data were identical to that of unmodifiedOH-Et-Sq.

TEM and photomicroscopy measurements indicated that theparticle/crystallite size of the squaraine composition prepared inaccordance with Example V was less than 10 percent of the originalparticle/crystallite size of the untreated, or unmodifiedbis(2-hydroxy-4-N,N-diethylaminophenyl)squaraine. This reduction inparticle size enables more uniform dispersion, or coverage of thehydroxy squaraine in the photoconductive layer, when these compositionsare incorporated into imaging members.

EXAMPLE VI

The process of Example V was repeated with the exception that there wasselected as the squaraine reactant, O-TMS-Me(methyl)Sq,bis(2-hydroxy-6-methyl-4-N,N-diethylaminophenyl)squaraine, prepared inaccordance with Example III (0.1749 grams), with the hydrolysis solventsbeing methanol (10.0 ml) and water (0.5 ml). The resulting mixture wasstirred at 22° C. for 3 hours. After rinsing the isolated product with a20 percent solution of water in methanol, there was recovered as a lightgreen powder the modified squaraine OH-Me-Sq (0.131 grams). Infrared(Nujol) data was identical to that of unmodified OH-Me-Sq. The modifiedOH-Me-Sq has needle-like particles/crystallites 0.5-1.0 um in length,and 0.1 um wide as compared with the unmodified OH-Me-Sq which has aparticle/crystallite size of 100 um in length and 20 um wide, asdetermined by TEM, and photomicroscopy.

In the following examples there is detailed the preparation ofphotoresponsive imaging members by coating dispersions ofphotoconductive pigments in polymeric binders, and the coating ofpolymeric solutions of the charge transport molecule indicated, onaluminized Mylar, which is about 3 mils in thickness. Moreover in all ofthe examples the aluminized Mylar was overcoated in a thickness of 0.05um., with an adhesive material of the polyester duPont 49,000. Mylar isa tradename for a poly(ethylene terephthalate) film available fromduPont. In each example the charge transport molecule selected wasN,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine, 40weight percent, dispersed in 60 percent by weight of the polycarbonateMakrolon, dissolved in dichloromethane. For the coating of the solutionsthere was selected a known Bird applicator.

EXAMPLE VII

A dispersion of photoconductive pigment was prepared by adding 0.100grams of the unmodified squaraine composition OH-Sq, and 50 grams of 1/8inch No. 302 stainless steel shot to a solution of 0.400 grams ofGoodyear Vitel PE-200 polyester resin and 8.0 ml of dichloromethane in a2 oz. bottle followed by shaking the resulting mixture on a paintshaker. The pigment dispersion product was then coated onto analuminized Mylar substrate with a 1.0 mil gap Bird-type applicator bar.The coating was air-dried and followed by drying under vacuum at 100° C.for 2.5 hours.

There was then coated on the above prepared photoconductive layer with aBird applicator a charge transport layer containing 40 percent by weightof N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine,dispersed in 60 percent by weight of the polycarbonate resinous binderMakrolon.

EXAMPLE VIII

A photoresponsive device was prepared by repeating the procedure ofExample VII with the exception that there was selected as thephotoconductive pigment the modified hydroxyl squaraine as prepared inExample IV in place of the unmodified hydroxyl squaraine.

EXAMPLE IX

A photoresponsive device was prepared by repeating the procedure ofExample VII with the exception that there was first coated with a Birdapplicator on the aluminized Mylar substrate a photogenerating layercontaining trigonal selenium dispersed in a poly(N-vinylcarbazole)solution. This photogenerating layer was prepared by dispersing 7.5volume percent of finely milled trigonal selenium in apoly(N-vinylcarbazole) solution containing a mixture oftetrahydrofuran:toluene (1:1). The thickness of this layer was about twomicrons.

EXAMPLE X

A photoresponsive device was prepared by repeating the procedure ofExample IX with the exception that there was selected as thephotoconductive pigment, 0.1 grams, of the modified hydroxyl squaraineas prepared in accordance with Example IV.

EXAMPLE XI

A photoresponsive device was prepared by repeating the procedure ofExample VII with the exception that there 0.126 grams of unmodifiedhydroxyl squaraine was selected, and there was used as the pigmentbinder resin, PE-100 polyester (0.380 grams), available from GoodyearChemical.

EXAMPLE XII

A photoresponsive device was prepared by repeating the procedure ofExample VII with the exception that 0.126 grams of a modified hydroxylsquaraine as prepared in accordance with Example IV was selected, and inplace of PE-200 there was selected the polyester PE-100 (0.380 grams).

EXAMPLE XIII

A photoresponsive device was prepared by repeating the procedure ofExample VII with the exception that there was first coated on thealuminized Mylar substrate, a hole transport layer containing thespecific diamine indicated, followed by coating thereover a polymericdispersion of a photoconductive hydroxyl squaraine pigment.

EXAMPLE XIV

A photoresponsive device was prepared by repeating the procedure ofExample XIII with the exception that there was selected 0.12 grams ofthe modified hydroxyl squaraine as prepared in accordance with theprocedure of Example IV, as a replacement for the unmodified hydroxylsquaraine.

EXAMPLE XV

A photoresponsive device was prepared by repeating the procedure ofExample XIII with the exception that 0.166 grams of the unmodifiedhydroxyl squaraine was selected, and 0.3808 grams of the polycarbonateMakrolon was used as a replacement for the PE-200 composition.

EXAMPLE XVI

A photoresponsive device was prepared by repeating the procedure ofExample XIII with the exception that 0.177 grams of the modifiedhydroxyl squaraine as prepared in accordance with Example IV wasselected, and 0.3808 grams of the resinous polycarbonate binder Makrolonwas used as a replacement for the PE-200 composition.

Several of the above prepared photoresponsive devices were thenelectrically tested by charging them with a constant voltage corotronand photodischarging the devices with a specific wavelength (for example597 nm or 800 nm light.) The charging and photodischarging processeswere monitored by an electrometer and recorded on a strip chartrecorder. The surface potential of the photoresponsive device just priorto the light exposure is represented by V_(DDP). The maximum sensitivitywas calculated as the maximum photodischarge rate divided by the radiantpower of the light, and the energy to 1/2 V_(DDP) was the light energyrequired to discharge the device to 1/2 of its original surfacepotential value.

    ______________________________________                                        ELECTRICAL DATA OF PHOTORECEPTORS                                             CONTAINING MODIFIED AND UNMODIFIED                                            HYDROXYL SQUARAINE (OH.Sq)                                                    SURFACE      MAXIMUM       ENERGY to                                          POTENTIAL    SENSITIVITY   1/2 V.sub.DDP.spsb.1                                      V.    V-Cm.sup.2 /Erg                                                                             Erg/cm.sup.2                                       EXAMPLE  V.sub.DDP                                                                             at 597 nm                                                                              at 800 nm                                                                            at 597 nm                                                                            at 800 nm                             ______________________________________                                        VII      -895    37.1     42.2   14.9   13.11                                 a,c,f,i                                                                       VIII     -895    63.4     86.8   8.35   6.18                                  b,c,f,i                                                                       IX       -900    52.9     58.6   10.0   10.6                                  a,d,f,i                                                                       X        -895    74.8     94.4   7.43   6.36                                  b,d,f,i                                                                       XI       -900    41.9     51.4   12.8   10.8                                  a,c,g,j                                                                       XII      -895    87.4     116.6  6.19   4.79                                  b,c,g,j                                                                       XIII      900    40.4     37.0   13.6   15.0                                  a,e,f,i                                                                       XIV       895    43.6     49.1   13.6   13.3                                  b,e,f,i                                                                       XV        710    56.8     62.8   6.67   7.71                                  a,e,h,k                                                                       XVI       510    74.8     81.5   4.59   3.90                                  b,e,h,k                                                                       ______________________________________                                    

a is unmodified OH-Sq; b is modified (by the invention process) OH-Sq, cis configuration 1, d is configuration 3, e is configuration 2, f isweight loading of squaraine=20 percent, g is weight loading ofsquaraine=25 percent, h is weight loading of squaraine=30 percent, i isPE-200 binder, j is PE-100 binder, k is Makrolon binder, l is energyrequired to discharge one-half of the initial surface potential.

The larger the maximum sensitivity number the more desirable dischargeis achieved, that is, the discharge rate is greater with the same amountof light. A smaller value of energy to 1/2 V_(DDP) represents a moreefficient photodischarge.

EXAMPLE XVII

Bis(2-trimethylsilyloxy-4-N,N-dimethylaminophenyl)squaraine (O-TMS-Sq,0.250 gram) obtained by the process of Example I, was stirred underargon gas with deuterated methanol-d₁, (99.5 percent isotopic purity,11.0 ml) and deuterium oxide (99.96 percent isotopic purity, 0.50 ml),at 25° C. for 2.5 hours. The solid was collected by vacuum filtrationunder vacuum and rinsed with diethyl ether. The collected material wasdried under vacuum at 45° C. for 2 hours yielding 0.194 gram ofbis(2-deuteriohydroxy-4-N,N-dimethylaminophenyl)squaraine (deuteratedhydroxyl squaraine, OD-Sq) as a green solid.

Calcd for C₂₀ H₁₈ D₂ N₂ O₄ : 67.78; H and D, 6.26;

Found: C, 67.86; H and D, 6.65.

EXAMPLE XVIII

A photoresponsive device was prepared by repeating the procedure ofExample VII with the exception that thebis-(2-deuteriohydroxy-4-dimethylaminophenyl)squaraine, obtained by theprocess of Example XVII, (OD-Sq), 0.100 grams, was selected in place ofthe unmodified hydroxyl squaraine.

EXAMPLE XIX

A photoresponsive device was prepared by repeating the procedure ofExample IX with the exception that there was selected as thephotoconductive pigment 0.100 grams of the deuterated hydroxyl squaraineOD-Sq, obtained by the process of Example XVII, in place of theunmodified hydroxyl squaraine.

EXAMPLE XX

A photoresponsive device was prepared by repeating the procedure ofExample XIII with the exception that 0.100 grams of the deuteratedhydroxyl squaraine, OD-Sq, obtained by the process of Example XVII, wasselected in place of the unmodified hydroxyl squaraine.

Electrical tests were conducted for the devices Examples XVIII and XIXwith the following results:

    ______________________________________                                        ELECTRICAL DATA OF PHOTORECEPTORS                                             CONTAINING DEUTERATED HYDROXYL-d.sub.2 -SQUARAINE                             (compound obtained from Example XVII)                                         SURFACE      MAXIMUM       ENERGY to                                          POTENTIAL    SENSITIVITY   1/2 V.sub.DDP                                             V     V-Cm.sup.2 /Erg                                                                             Erg/Cm.sup.2                                       EXAMPLE  V.sub.DDP                                                                             at 597 nm                                                                              at 800 nm                                                                            at 597 nm                                                                            at 800 nm                             ______________________________________                                        XIII.sup.a                                                                             -890    56.4     73.3   9.52   7.47                                  XIX.sup.b                                                                              -885    64.7     84.1   9.19   7.19                                  XX.sup.c  907    30.1     34.1   21.8   23.4                                  ______________________________________                                         .sup.a configuration 1,                                                       .sup.b configuration 3,                                                       .sup.c configuration 2.                                                  

Although the invention has been described with reference to specificembodiments, it is not intended to be limited thereto, rather thoseskilled in the art will recognize that variations and modifications maybe made therein which are within the spirit of the present invention andwithin the scope of the following claims.

We claim:
 1. Silylated compositions of matter selected from the groupconsisting of: ##STR3## wherein R₁ and R₂ are independently selectedfrom alkyl groups, aromatic groups, cyclic groups, and non-cyclicgroups, R₃, R₄ and R₅ are selected from the group consisting ofhydrogen, alkyl groups, halides, alkoxy, alkyl carboxy, R₆, R₇ and R₈are selected from the group consisting of alkyl substituents,halogenated substituents, and oxygenated substituents, and X is selectedfrom the group consisting of oxygen, sulfur, and selenium, R'₁, R'₂,R'₃, and R'₄, are independently selected from alkyl groups, aromaticgroups, cyclic groups, and non-cyclic groups, providing that at leastone of these groups is dissimilar, R'₅, R'₆, R'₇, R'₈, R'₉, R'₁₀, andR'₁₁, are independently selected from the groups consisting of hydrogen,alkyl groups, halides, alkoxy, and alkyl carboxy, and R'₁₂, R'₁₃, andR'₁₄, are independently selected from the groups consisting of alkylsubstituents, halogenated substituents, and oxygenated substituents. 2.A composition in accordance with claim 1 wherein R₁, R₂, R₃, R₄, R₅, R₆,R₇, and R₈ are alkyl groups of from about 1 carbon atom to about 6carbon atoms.
 3. A composition in accordance with claim 1 wherein R₁ andR₂ are selected from the group consisting of methyl, and phenyl.
 4. Acomposition in accordance with claim 1 wherein R₃, R₄, and R₅ arehydrogen.
 5. A composition in accordance with claim 1 wherein R₁, R₂,R₆, R₇, and R₈ are methyl, R₃, R₄, and R₅ are hydrogen, and X is oxygen.6. A composition in accordance with claim 1 wherein X is oxygen.
 7. Acomposition in accordance with claim 1 wherein R'₁, R'₂, are methyl, andR'₃, and R'₄ are ethyl.
 8. Deuterated hydroxyl squaraine derivativesselected from the group consisting of: ##STR4## wherein R₁ and R₂ areindependently selected from alkyl groups, aromatic groups, cyclicgroups, and non-cyclic groups, R₃, R₄ and R₅ are selected from the groupconsisting of hydrogen, alkyl groups, halides, alkoxy, alkyl carboxy, Xis selected from the group consisting of oxygen, sulfur, and selenium, Dis a deuterium atom, R'₁, R'₂, R'₃, and R'₄ are independently selectedfrom alkyl groups, aromatic groups, cyclic groups, and non-cyclic group,providing that at least one of these groups is dissimilar R'₅, R'₆, R'₇,R'₈, R'₉, R'₁₀, and R'₁₁, are independently selected from the groupsconsisting of hydrogen, alkyl groups, halides, alkoxy, and alkylcarboxy, R'₁₂, R'₁₃, and R'₁₄, are independently selected from thegroups consisting of alkyl substituents, halogenated substituents, andoxygenated substituents.
 9. A composition in accordance with claim 8wherein R₁ and R₂ are alkyl groups of from about 1 carbon atom to about6 carbon atoms.
 10. A composition in accordance with claim 8 wherein R₃,R₄ and R₅ are alkyl groups of from about 1 carbon atom to about 6 carbonatoms.
 11. A composition in accordance with claim 8 wherein the R₁, andR₂ substituents are methyl or phenyl.
 12. A composition in accordancewith claim 8 wherein R₃, R₄, and R₅ are hydrogen.
 13. A composition inaccordance with claim 8 wherein R₁, and R₂ are methyl, R₃, R₄, and R₅are hydrogen, D is deuterium, and X is oxygen.
 14. A composition inaccordance with claim 8 wherein X is oxygen, sulfur, or selenium.
 15. Acomposition in accordance with claim 8 wherein R'₁, and R'₂ are methyl,and R'₃, and R'₄ are ethyl.
 16. A composition in accordance with claim 1wherein R₁ and R₂ are methyl.
 17. A composition in accordance with claim1 wherein R₃ and R₄ are ethyl.
 18. A composition in accordance withclaim 1 wherein X is selenium.
 19. A composition in accordance withclaim 1 wherein X is sulfur.